1. Field of the Invention
This invention relates to a process for the recovery of vanadium from carbonaceous materials. In one of its more particular aspects, this invention relates to using a molten salt treatment for recovering vanadium values from carbonaceous materials derived from petroleum.
2. Prior Art
Vanadium is the most abundant trace metal present in petroleum, occurring in crude petroleum in the range of about 0.001% by weight to about 0.15% or more depending upon the source of petroleum. The petroleum containing the highest concentrations of vanadium occurs in Venezuela. Some processed Venezuelan petroleum residues, such as coke, for example, have been found to have a vanadium concentration of as high as about 5% by weight. Because of the economic value of vanadium, attempts have been made in the past to recover the vanadium present in petroleum.
U.S. Pat. No. 2,383,972 discloses a process for recovering vanadium from petroleum during the course of a cracking operation which comprises reacting the metallic constituents of petroleum oil, including vanadium, with a solid hydrated sodium aluminum silicate of the zeolite type. Vanadium is recovered from the zeolite by means of solvent treating the zeolite with a strong mineral acid, precipitating the vanadium as ammonium vanadate by evaporating the acid solution with an excess of ammonium chloride, roasting the ammonium vanadate to produce the oxide, and reducing the oxide in an electric furnace.
Removal of traces of vanadium and other metals has also been of interest in processing hydrocarbon feedstocks. U.S. Pat. No. 2,990,365 discloses a process for demetallizing hydrocarbon oils by modifying the properties of complex organometallic compounds, including vanadium organometallics occurring in the oils, by contacting the hydrocarbon oils in the liquid phase with a fused alkali metal hydroxide. The organometallic compounds present are thereby converted to alkali metal salts which have greater water solubility and can be more easily removed from the hydrocarbon oils than the organometallic compounds.
U.S. Pat. No. 3,936,371 discloses a process for the removal of metal contaminants from heavy hydrocarbon oils by means of treatment with "red mud," a residue which occurs when bauxite is dissolved at high temperatures to produce alumina as a raw material for the electrolytic production of aluminum. Contacting the hydrocarbon oil with the "red mud" at temperatures in the range of about 350.degree. to 500.degree. C. in the presence of hydrogen at a pressure of about 1 to 300 atmospheres is said to be highly effective in removing the vanadium and other contaminants from the hydrocarbon oil.
U.S. Pat. No. 4,003,823 discloses a process for simultaneously desulfurizing and demetallizing heavy hydrocarbon feedstocks by a hydroconversion process utilizing an alkali metal hydroxide and hydrogen at a pressure of about 500 to 5000 psig and a temperature in the range of about 500.degree. to 2000.degree. F. (260.degree. to 1093.degree. C.).
U.S. Pat. No. 4,119,528 discloses a process in which simultaneous desulfurization, demetallization, and hydroconversion of heavy carbonaceous feeds is accomplished by treatment with potassium sulfide and hydrogen. The process is carried out at a temperature in the range of about 500.degree. to 2000.degree. F. (260.degree. to 1093.degree. C.) and a hydrogen pressure of about 500 to 5000 psig.
These prior art processes are generally designed to remove metallic impurities from hydrocarbonaceous feedstocks and do not result in rendering vanadium values readily recoverable from such processed feedstocks.
Recently, the use of molten salts for processing carbonaceous materials and for conducting a variety of chemical reactions has been suggested. U.S. Pat. No. 3,708,270 discloses a process in which carbonaceous materials are pyrolyzed by contact with a hot sulfate- or sulfide-containing melt under nonoxidizing conditions to produce valuable effluent combustible gases and char.
In U.S. Pat. No. 3,916,617, there is disclosed a process for gasification of a carbonaceous material to produce a combustible gas containing a high proportion of carbon monoxide to carbon dioxide. The resulting low Btu gas can be used as an energy source for conventional boilers, for example.
U.S. Pat. No. 3,899,322 discloses a process for recovering valuable metals from scrap containing metal values by means of a molten salt treatment using an alkali metal carbonate and optionally an alkali metal sulfate. A molten salt pool is maintained at a temperature in the range of about 400.degree. to 1800.degree. C. Excess air is passed into the pool, and the molten metal is removed from below the molten salt pool. The process is said to be particularly useful for recovering noble-type metals such as copper, silver, gold, palladium, and platinum, and also aluminum, from scrap containing such metal values.
In U.S. Pat. No. 4,164,416, there is disclosed a process for recovering metallic copper or lead from a sulfide ore containing the same by reacting the sulfide ore with a carbonaceous material and gaseous oxygen in a molten alkali metal carbonate pool. Temperatures in the range of about 600.degree. to 1350.degree. C. are utilized to cause reduction of the metal sulfide to metallic copper or lead.
None of the foregoing processes, however, can be used to recover vanadium values from carbonaceous materials.